Thermally stabilized liquid hydrocarbon fuels



United States Patent Delaware No Drawing. Filed July 21, 1961, Ser. No. 125,673 15 Claims. (Cl. 44-62) This invention relates to improving the thermal stability of liquid hydrocarbon fuels boiling in the combustion gas turbine fuel range. More particularly, the invention relates to reducing the tendencies of such fuels toward forming solid deposits at very high service temperatures by incorporating therein small amounts of oilsoluble, boron-containing copolymers.

Combustion gas turbine fuel is presently employed as a cooling medium, or heat sink, in some combustion gas turbine powered aircraft in order to remove heat by indirect heat exchange from hot lubricating oil that has absorbed heat developed in the engine by compression of combustion air, by fuel combustion, and by friction of moving parts. As a result, the fuel is subjected during service to heat transfer surface temperatures of the order of 300 to 400 F. for relatively substantial time intervals. In addition, the fuel may be subjected to even higher temperatures, of the order of 500 F., for short periods of time in the area of the nozzles or orifices from which the fuelis introduced into the combustion chamber of the engine. As a result of exposure to these high temperatures, certain components of the fuel tend to undergo decomposition due to polymerization, oxidation, and thermal decomposition, and to form solid or semi-solid degradatin products that clog the fuel orifices and thereby interfere with proper combustion of the fuel and proper operation of the engine. Ordinary stabilizing agents, antioxidants, and the like, of the kind that are employed to stabilize the fuels during storage have been found inadequate to inhibit deterioration of the fuels at temperatures of the magnitude encountered in the vicinity of the heat transfer surfaces of aviation turbine engines, thus indicating a difference in kind between low or moderate temperature deposits, that is, deposits formed below 300 F. and the high temperature deposits with which the present invention is concerned.

The present invention relates to improving the thermal stability of liquid hydrocarbon distillate fuels boiling in the combustion gas turbine fuel range, such as aviation turbine fuel, and to reducing the tendencies of such fuels to form deposits on heat transfer surfaces at temperatures in excess of 350 F. and in the fuel inlet regions of the combustion zones of the engines in which the fuels are consumed, whereby such fuels are rendered more suitable for use in these engines. it has been found that the thermal stability characteristics of these fuels can be improved by incorporating therein a small amount of an oil-soluble boron-containing copolymer of monomeric components that each contain a copolymerizable ethylenic linkage, and at least one of which is a boronfree material and contains an oleophilic, saturated aliphatic hydrocarbon substituent containing 8 to 18 and preferably 12 to 18 carbon atoms. Especially good results are obtainable with higher fatty esters of lower, alpha-beta unsaturated monocarboxylic acids, such as acrylic acid or a lower alpha-alkacrylic acid. An example of a preferred boron-free monomer is lauryl methacrylate, but other materials can be used. Another of the monomeric components from which the oil-soluble boron-containing copolymer is derived is a diester of a boronic acid whose boronyl substituent is a hydrocarbon 5,150,470 Patented Dec. 1, 1964 radical containing 2 to 18 carbon atoms. Excellent results are obtainable when the boronyl substituent is a saturated aliphatic hydrocarbon radical or an aryl radical, including aralkyl and alkaryl, containing 6 to -18 carbon atoms. Examples of preferred boronyl substituents are the nonyl and phenyl radicals, but the invention is not limited to these particular substituents. For example, the boronyl substituent can be butyl or cyclohexyl or other hydrocarbon radicals as indicated. At least one of the ester substituents of the boronic acid diester is an unsaturated aliphatic hydrocarbon radical containing 2 to 12, and preferably 2 to 4, carbon atoms and an ethylenic linkage that is copolymerizable with the ethylenic linkage of the boron-free monomeric component. A preferred ester substituent is the allyl group, but other substituents of the indicated class are also suitable. The other ester substituents of the boronic acid diester is either a radical of the same kind, as is preferred, or another hydrocarbon radical co ntaining 1 to 18 carbon atoms. Exceptionally good results are obtained when the boron-containing copolymers also contain as one of the monomeric components a nitrogenous monomer having an ethylenic linkage that is copolymerizable with the ethylenic linkages of the above-described boron-containing and boron-free monomeric components and having an organic, nitrogenous substituent that has as at least one of its N-substituents a hydrocarbon radical containing 1 to 18 carbon atoms. 'Especially good results are obtainable with nitrogenous esters of lower, alpha beta unsaturated. monocarboxylic acids and alkylolamines whose alkylol substituents contain not more than seven carbon atoms. These esters of alkylolamines Whose alkylol substituents contain 2 to 4 carbon atoms are eifective. An example of a preferred material is di(Oxooctyl)aminoethyl methacrylate. However, other nitrogenous copolymerizable monomers of the class indicated can be used. The monomeric boron-containing component is present in the copolymers of this invention in weight ratios of about 0.03 to 1:1 with respect to the other boron-free monomeric component or components. In the case of the two-component copolymers, the boroncontaining and the boron-free monomeric components are preferably present in a weight ratio of about 0.05:1 to 0.75:1. Where a nitrogenous monomeric component is additionally included, it is also preferably employe in similar weight ratios as the boron-containing component. An example of an especially advantageous copolymer is the 0.12:0.12z1 Weight ratio terpolymer of diallyl nonylboronate, di(Oxo-octyl)-aminoethyl methacrylate and lauryl methacrylate, but other copolymers prepared with other monomer weight ratios Within the range indicated can be used. The boron-containing copolymers Whose use is included by this invention are effective thermal stabilizers when employed in hydrocarbon fuels in small amounts. Proportions in the range of 10 to 20 pounds per 1,000 barrels of hydrocarbon fuel are preferred, but other proportions, for example, about 2.5 to 50 pounds or more per thousand barrels of fuel, can be used. Although the above-described nitrogenous copolymers are especially advantageous from the standpoint of controlling the thermal stability of hydrocarbon disas the preferred boron-containing copolymers disclosed herein can effect a reduction not only in fuel nozzle deposits but also in heat transfer surface deposits, notwithstanding the fact that the two kinds of deposits differ chemically and physically from each other, and notwithstanding that both of these types of deposits are not normally controllable by the same addition agent, it follows that the boron-containing copolymers described herein must function in at least two distinct ways.

The boron-containing copolymers disclosed herein can be prepared in any convenient way. For example, they can be prepared as described in copending application Serial No. 125,672, filed July 21, 1961, in the name of Phillip G. Abend. Very briefly, in accordance with the method disclosed in that application, the copolymers described herein can be prepared by reacting the boroncontaining monomer and the nitrogenous monomer, when the latter is desired, in the indicated weight ratios, in the presence of a diluent, preferably a solvent, such as toluene, benzene, ethyl acetate, or other solvents having similar chain transfer activity, at a temperature in the range of 7S C. to 150 0., preferably 25 C. to 150 C., in the presence of a few hundredths percent to 2 percent, preferably 0.2 to 1.0 percent, of a free radical catalyst such as benzoyl peroxide, lauroyl peroxide, or alpha,alpha'-azodiisobutyronitrile, preferably in the substantial absence of oxygen, until the rate of formation of larger polymer molecules has declined substantially, usually after about 30 minutes to 35 hours. The time at which the reaction may be terminated is determinable by periodic sampling of the reaction mixture and observing for a decline in the rate of increase in viscosity (or molecular weight) of the mixture. Alternatively, instead of the procedure described above, conventional bulk or dispersion polymerization methods can be used, as can other conventional polymerization catalysts.

The boron-free monomers from which the boron-containing copolymers described herein are derived can be any unsaturated compound containing a copolymerizable, carbon-to-carbon double bond and having an oleophilic extralinear (with respect to the copolymer) substituent containing 8 to 18 carbon atoms, especially 12 to 18 carbon atoms, preferably where at least six of the carbon atoms are in a straight chain. The extralinear substituent can be linked to the polymerizable portion of the monomer molecule through other than a carbon-to-carbon linkage. For example, such substituents can be linked to the polymerizable portion of the monomer molecule through linkages involving nitrogen, oxygen, sulfur, and/ or phosphorus, as for example in the case of esters, ethers, or the like. Excellent copolymers are obtainable from higher fatty esters of acrylic or lower alpha-alkacrylic acids, of which lauryl methacrylate is a preferred example. The expresison higher fatty esters is used in its usual sense to indicate an aliphatic hydrocarbon substituent containing 8 or more carbon atoms. Specific examples of other boron-free monomers useful in the preparation of the herein-described copolymers include other long-chain saturated and unsaturated esters of acrylic or lower alpha-alkacrylic or other copolymeriza ble, lower, alpha-beta unsaturated monocarboxylic acids, particularly the 3 to carbon atom acids, such as octyl acrylate, oleyl methacrylate, or the lauryl esters of crotonic, tiglic, angelic, and senecioic acids, or corresponding esters of alpha-beta unsaturated dicarboxylic acids, such as methyl lauryl fumarate and dioctyl maleate. Still other boron-free ethylenically unsaturated monomers that are useful in the preparation of the herein-described copolymers include esters of ethylenically unsaturated alcohols and long-chain fatty acids such as vinyl stearate, vinylphenyl oleate, unsaturated ethers such as vinyl octyl ether and vinyl lauryl ether, unsaturated thioethers such as vinyl lauryl sulfide, and mono-olefins such as 1- octene, l-nonene, and l-dodecene. The boron-free unsaturated monomers, like the other monomers disclosed herein, can be employed individually or in various combinations. The boron-free monomers described above normally form the chief component of the hereindescribed copolymers in order to insure oil-soluble characteristics in the latter.

The boron-containing monomers from which the copolymers disclosed herein can be prepared can be any unsaturated diester of a boronic acid whose boronyl substituent is a hydrocarbon radical containing 2 to 18 carbon atoms and having as at least one ester substituent an aliphatic hydrocarbon radical that contains 2 to 12 carbon atoms and that contains an ethylenic linkage that is copolymerizable with that of the boron-free monomeric component, and that has as its other ester substituent either a radical of the same kind or another hydrocarbon radical containing 1 to 18 carbon atoms. The aliphatic hydrocarbon ester substituents can be unsubstituted or substituted with nonhydrocarbon substituents, such as oxygen, nitrogen, sulfur, halogen or the like, provided that such substituents do not interfere with the copolymerization reaction or with the thermal stabilizing properties of the copolymers. Examples of substituents of this kind are the furfuryl radical and alkylaminoalkyl radicals such as the diethylaminoethyl group. Boronic acid esters whose boronyl substituents are saturated aliphatic hydrocarbon radicals, including cycle-aliphatic configurations, or aromatic hydrocarbon radicals are preferred, as the presence of these noncopolymerizable radicals tend to minimize excessive cross-linking. Thus, good results are obtainable with boronic acid esters whose boronyl substituents are alkyl radicals such as ethyl or butyl, but we prefer those esters whose boronyl substituents contain 6 to 18 carbon atoms, such as octyl, nonyl, octadecyl, cyclohexyl, methylcyclohexyl, or aryl groups containing the same number of carbon atoms, including alkaryl and aralkyl radicals, such as phenyl, naphthyl, tolyl, dodecylphenyl, benzyl, methylbenzyl, decylbenzyl or the like. Boronic acid esters can be used having as one ester substituent an unsaturated, copolymerizable radical, particularly alkenyl groups containing 2 to 4 carbon atoms, such as vinyl, allyl, crotyl, or, alternatively a higher alkenyl group such as l-dodecenyl, or an unsaturated heterocyclic radical such as furfuryl or the like, and having as the other ester substituent either an ethylenically unsaturated hydrocarbon radical of the same kind or some other hydrocarbon radical containing 1 to 18 carbon atoms, such as methyl or butyl, or a radical of the same kind as the boronyl substituent. Preferably, the second ester substituent is a radical like the firstmentioned ester substituent, such as allyl, but this is not necessary. Excellent results are obtainable when the boronyl substituent is nonyl or phenyl, and when the ester substituents are allyl groups, specific examples of such materials being diallyl nonylboronate and diallyl phenylboronate. Examples of other boronic acid diesters are diallyl cyclohexylboronate, divinyl butylboronate, diallyl butylboronate, butylallyl butylboronate, and dicrotyl nonylboronate.

Nitrogenous monomers capable of forming ternary copolymers described herein are monomeric unsaturated compounds containing an ethylenic linkage that is copolymerizable with the ethylenic linkage of each of the above-described boron-free and boron-containing monomeric components and containing an organic, nitrogencontaining substituent group that does not of itself copolymerize with the ethylenic linkages of the boronfree and boron-containing monomers. The organic, nitrogen-containing substituents are characterized by the presence of at least one hydrocarbon N-substituent containing 1 to 18 carbon atoms, which substituent can be unsubstituted or substituted with nonhydrocarbon components such as oxygen, sulfur, or halogen, provided that such components do not unduly hinder copolymerization or adversely affect the stabilizing properties of the ultimate c opolymer. Oleophilic substituents such as aliphatic hydrocarbon radicals containing 8 to 18 carbon atoms or aralkyl radicals containing 7 to 23 carbon atoms are advantageous, but other hydrocarbon radicals, for example, ethyl and propyl are satisfactory. The organic, nitrogen-containing substituent group can be associated with the copolymerizable portion of the nitrogenous monomer molecule in various ways. For example, these substituents are preferably linked to the monomer chain through an ester linkage. However, the N-substituents can be linked to the monomer chain in other ways, as

by salt linkages, including both quaternary ammonium salt and addition salt linkages, as well as those involving dehydrated addition salt, i.e., amide, linkages.

When the organic, nitrogen-containing substituent of the nitrogenous monomer from which the preferred copolymers are derivable is associated with the copolymerizable portion of the monomer molecule through an ester linkage, as is preferred, the nitrogen-containing monomer can be a monomeric ester of a copolymerizable, lower alpha-beta unsaturated monocarboxylic acid such as acrylic acid or a lower alpha-alkacrylic acid such as methacrylic acid, or some other lower, alpha beta unsaturated monocarboxylic acid, particularly the 3 to 5 carbon atom acids, such as crotonic, angelic or tiglic acids, and an amine having as at least one N-substituent an alkylol group, normally containing 2 to 4 carbon atoms, such as ethylol or propylol. The other N-substituents can be aliphatic hydrocarbon radicals containing 1 to 18 carbon atoms, preferably 8 to 18 carbon atoms, such as Oxo-octyl, lauryl, myristyl, n-hexadecyl, n-octadecyl, n-octadecenyl, or n-octadecadienyl, or hydrogen. It is preferred that at least one of such other N-substituents be a hydrocarbon radical. A specific example of a preferred nitrogenous unsaturated monomer in which the nitrogen-containing substituent is linked to the copolymerizable portion of the monomer molecule through an ester linkage is di(0xooctyl)aminoethyl methacrylate. Specific examples of other such monomers are diethylaminoethyl, n-octylaminoethyl, laurylarninoethyl, octadecylaminoethyl, and octadecenylaminoethyl acrylates, methacrylates, and crotonates.

When the nitrogenous substituents are linked to the copolymerizable portion of the monomer through a quaternary ammonium salt linkage, the nitrogenous monomer can be the quaternary ammonium salt of one of the abovedescribed copolymerizable lower alpha-beta unsaturated monocarboxylic acids, one of whose four covalent N- bonds is preferably attached to a monovalent aliphatic hydrocarbon radical containing 8 to 18 and more preferably 12 to 18 carbon atoms, such as lauryl, myristyl, n-hexadecyl, n-octadecyl, n-octadecenyl, or n-octadecadienyl, the other of whose covalent ,N-bonds are attached to the same or dilferent monovalent aliphatic hydrocarbon radicals containing 1 to 18 carbon atoms, such as methyl, ethyl, propyl, or butyl, or aralkyl radicals containing 7 to 23 carbon atoms, such as benzyl, tolylethyl, or a polypropylated aralkyl radical such as p-tetrapropylbenzyl. A specific example of -a preferred unsaturated quaternary ammonium salt monomeric component is mixed octadecenyland octadecadienyltrimethylammonium methacrylate. Examples of other such monomeric components are distearyldimethylammonium, dioctadecenylidimethylammonium, octadecenyldimethylethylammonium, distearylidimethylammonium, laurylbenzyldimethylammonium, lauryldimethyl- (ethylbenzyl)ammonium acrylates, methacrylates, and crotonates. 1

When the nitrogen-containing substituent group is attached to the copolymerizable unsaturated portion of the monomeric component through an addition salt linkage or the like, the nitrogen-containing monomeric component can be a salt of one of the above-described copolymerizable, lower alpha-beta unsaturated monocarboxylic acids and an amine having as at least one N-substituent an aliphatic hydrocarbon radical, preferably containing 8 to 18 carbon atoms, especially 12 to 18 carbon atoms, such as lauryl, myristyl, n-hexadecyl, n-octadecyl, or n-octadecadienyl. The other N-substituents can be the same as or different from the first-mentioned N-substituent. For example, the other N-substituents can be hydrogen, aliphatic hydrocarbon radicals cotaining 1 to 18 carbon atoms, such as methyl, propyl, butyl, or a radical of the same kind as the first-mentioned N-substituent, or alkylol groups containing l to 4 carbon atoms, such as ethylol or propylol. An example of a preferred unsaturated monomeric component in which the nitrogen-containing substituent is linked to the polymerizable portion of the monomer molecule through an addition salt linkage is di(Oxo-octyl) am monium methacrylate. Examples of other such monomers are di(Oxo-octyl) ammonium, di(Oxo-octyl)hydroxyethylammonium, octylammonium, dioctylammonium, trioctylammonium, laurylammonium, octadecylammonium, and octadecenylammonium acrylates, methacrylates, and crotonates.

The herein-described copolymers can be derived not only from the boroncontaining, and the boron-free, unsaturated monomeric compounds described above, but also they can be derived from one or more additional monomeric compounds copolymerizable therewith that may or may not contribute to the oil-solubility or thermal stabilitypromoting properties of the copolymers, provided that the proportions of these additional monomeric compounds are such as not to diminish significantly the desired thermal stabilizing and minimum oil-solubility properties of the copolymers. Examples of such compounds include ethylenically unsaturated copolymerizable monomers such as vinyl, allyl and crotyl acetates, butyrates, and the like, ethylene, propylene, l-butene, styrene, acrylic acid, acrylonitrile, or the like. The preferred copolymers disclosed herein are those in which the boron-containing monomer and the nitrogen-containing monomer, if desired, are present, respectively, in the ultimate copolymer in weight ratios in the range of about 0.05 to 0.75 part by weight to 1 part by weight of the other boron-free monomeric compound, but copolymers derived from these monomers in other weight ratios can be used, for example, copolymers can be used involving weight ratios in the range of about 0.03 to 1 part by weight of boron-containing and nitrogen-containing monomer to 1 part by weight of said other boron-free monomer.

The average molecular weight of the copolymers disclosed herein will normally be greater than about 2,000, and preferably greater than about 7,500, as determined by conventional methods. Usually, the average molecular weight of the copolymers will not exceed about 500,000, but the molecular weights canbe greater, provided that they are not so great as to render the copolymers insoluble in the liquid hydrocarbon fuel distillates disclosed herein. Copolymers within the preferred molecular weight range are characterized by intrinsic viscosities in the range of about 0.15 to about 0.75 deciliter per gram.

The herein-described copolymers can be incorporated in the liquid hydrocarbon fuels disclosed herein in any suitable manner. For example, they can be added to the fuel either as such or in diluted form promptly after distillation of the fuel or after storage at normal atmospheric temperatures for an indefinite period of time. Alternatively, the copolymers disclosed herein can be added to the fuels in admixture with other addition agents adapted to improve one or more characteristics of fuels. For example, the copolymer addition agents disclosed herein can be added to the fuels in admixture with corrosion inhibitors or conventional antioxidants.

, The copolymers disclosed herein can be employed in hydrocarbon distillate fuels that are to be subjected to temperatures above 300 F. in any proportion sufficient to improve the thermal stability of the latter. The eifective proportions of the various copolymers described herein may vary somewhat from member to member and also in accordance with the thermal stability of the uninhibited fuel. A noticeable improvement in thermal stability often will be obtained by the use of as little as 2.5 pounds of the copolymer per thousand barrels of fuel, but it is usually desirable to employ at least five pounds per thousand barrels of fuel in order to obtain a substantial improvement in thermal stability. A major improvement will ordinarily be obtained by the use of proportions in the range of about 10 to 20 pounds per thousand barrels of fuel. Although it is not usually necessary to exceed proportions of 20 pounds per thousand barrels of fuel, the herein-described copolymers can be employed in greater proportions, for example, up to 50 pounds or more per thousand barrels of fuel, in instances of fuels having unusually poor thermal stability characteristics, or in instances of relatively less effective copolymers.

Liquid hydrocarbon fuels of the kind whose use is included by this invention are hydrocarbon mixtures such as ordinary aviation turbine fuels, that is, jet fuels. The properties of the most common aviation turbine fuels are defined fully in the following specifications: MIL-J-S 161E (Referee JP-4 Fuel), MIL-J-5624D (JP-4, JP- Fuel), MIL-F-25656 (JP-6 Fuel), MIL-F-25524A (Thermally Stable Fuel), MIL-F-25558B (RI-1 Fuel), MIL-R 25576B (RP-1 Fuel), and ASTM D1655-59T. In general, aviation turbine fuels are characterized by the following common properties:

Gravity, API 32.5-57 Existent gum, mg./100 ml. (max.) 5-7 Potential gum, mg./100 ml. (max.) 4-14 Sulfur, percent (max.) 0.050.4 Mercaptan sulfur, percent (max.) 0001-0005 Freezing point, F. (max.) -75 to '40 Thermal value, B.t.u./lb. (min) l8,300-18,500 Aniline-gravity constant 4,500, usually 5,250 Aromatics, vol. percent (max.) 5-25 Olefins, vol. percent (max.) 15

In addition to these characteristics, it also may be noted that typical aviation turbine fuels employed for use in aviation turbine engines involving a high temperature fuel stability problem normally boil in the range of about 250 to 700 F., that is to say, these aviation turbine fuels normally boil above the gasoline range.

The ability of the materials disclosed herein to reduce formation of solid deposits in aviation turbine fuels at high service temperatures has been demonstrated by subjecting representative fuel compositions of the kind disclosed herien to the CFR Fuel Coker test procedure. This test procedure is described in detail in the Manual of ASTM Standards on Petroleum Products, ASTM D1660-59T. In accordance with this test method, aviation turbine fuels are subjected to flow conditions and temperature stresses similar to those in combustion gas turbine or jet aircraft engines by circulation through a simulated aircraft fuel system at a temperature above 300 F., at a rate of six pounds of fuel per hour, for a period of 300 minutes. The test apparatus comprises a fuel system containing two heated sections, one of which is a preheater section that simulates the hot fuel line sections of an aviation turbine engine as typified by the engine fuel-lubricating oil cooler. The extent of fouling of heat transfer surfaces in the preheater section by fuel degradation deposits is determined by inspection, and the extent of such fouling is used as one index of the high temperature stability of the aviation turbine fuel in the heat exchanger section of an aviation turbine engine. Preheater deposits are rated according to the following scale: 0=no visible deposits; 1=visible haze or dulling, but no visible color; 2=barely visible coloration; 3=light tan to peacock stain; 4=heavier than 3.

The second heated section comprises a filter section that simulates the nozzle area or fuel inlet area of the combustion zone of a jet engine Where fuel degradation particles may be trapped. A precision, sintered stainless steel filter is employed in the filter section to trap fuel degradation particles formed during the test. The extent of the buildup of fuel degradation particles in the filter section is indicated by the pressure differential across. the test filter, and this pressure differential is used as another index of the high temperature stability of the aviation turbine fuel. In carrying out the tests described, the temperature of the fuel at the outlet of the preheater section was maintained at 410 F and the filter section temperature was maintained at 500 F.

In the specific embodiments described herein the copolymers tested are identified, respetcively, as Copolymers A, B, C, D, E, and F. Copolymer A was a 0.12:0.12:l weight ratio tenpolymer of diallyl nonylboronate, diethylaminoethyl methacrylate and lauryl methacrylate prepared by reacting grams of lauryl methacrylate, 10 grams of diallyl nonylboronate and 10 grams of diethylaminoethyl methacrylate in the presence of 1 gram of alypha,alpha'-azodiisobutyronitrile as a catalyst, in 50 milliliters of toluene as a reaction solvent, at 65 to 70 C.,

with stirring, for about one and one-half hours. Solvent was removed by evaporation under reduced pressure when the reaction was complete. Analysis of the product was as follows:

Boron, percent 0.33 Neutralization value:

Total acid No 1.13 Total base No 30.83 Nitrogen, percent 1.07

Intrinsic viscosity, deciliter/ gram 0.21 Average molecular wt., Shear method 1 57,000i5,700

1 Method of Bueehe and Harding, Journal of Polymer Science, vol. XXYII, pages 177-186 (1958).

Copolymer B was a 0.122012: 1 weight ratio terpolymer of diallyl nonylboronate, di(Oxo-octyl)aminoethyl methacrylate and lauryl methacrylate prepared similarly as Copolymer A except that the reaction was carried out for only one hour.

Copolymer C was a 0.14:0.28:1 weight ratio terpolymer of diallyl nonylboronate, di(Oxo'octyl)aminoethyl methacrylate and lauryl methacrylate prepared similarly as Copolymer A except that the reaction was carried out at a temperature of 76 to 83 C. for one hour.

Copolymer D was a 0.12:0.12:l weight ratio terpolymer of diallyl phenylboronate, di(0xo-octyl)aminoethyl methacrylate and lauryl methacrylate prepared similarly as Copolymer A except that the reaction was carried out at a temperature .of 66 to 68 C. for two and one-half hours and at 76 to 79 C. for two and one-half hours.

Copolymer E was a 0.12:0.12:1 weight ratio terpolymer of diallyl butylboronate, di(Oxo-octyl)aminoethyl methacrylate and lauryl methacrylate prepared similarly as Copolymer A except that the reaction was carried out at 75 to 79 C. for five hours.

Copolymer F was a 0.25:1 weight ratio binary copolymer of diallyl cyclohexylboronate and laury l methacrylate prepared by reacting, with stirring, 40 grams of lauryl methacrylate, 10 grams of diallyl cyclohexylboronate, and 0.5 gram of alpha,alphasazodiisobutyronitrile, in solution in 25 milliliters of toluene, at about 72 to 77 F. for about five hours. Solvent was removed similarly as in the preparation of Copolymer A.

The Oxo-octyl substituents of the di(Oxo-octyl)aminoethyl methacrylate employed in the above-indicated copolymers were derived from Oxo-octyl alcohol, that is, mixed isomeric octyl alcohols prepared by the 0x0 synthesis process. A typical sample of Oxo-octyl alcohol of the kind from which the substituents were derived has been found to contain about 38 percent 4,5-dimethylhexyl alcohol, 30 percent 3,5-dimethylhexyl alcohol, 10 percent S-methylheptyl alcohol, 19 percent 3,4-dimethylhexyl alcohol, and 3 percent 5,5-dimethylhexyl alcohol.

In the tests described herein, the test fuels, hereinafter referred to, respectively, as Aviation Turbine Fuel 1 and Q Aviation Turbine Fuel 2, were commercial-type aviation turbine fuels having the following characteristics:

Aviation Aviation Turbine Turbine Fuel 1 Fuel 2 Gravity, API 43. 6 44. 3 Freezing Point, F -51 -56 Sulfur, L, percent.-. 0.054 0. 064 Mercaptan Sulfur, percent. 0. 001 0. 001 Existent Gum, rug/100 rnl 1. 6 1.0 Potential Gum, rug/100 ml- 5.2 3.0 Aromatics, Vol. percent 15. 7 14.0 Olefins, V01. percent. 1. 7 0.9 saturates, Vol. percent. 82.6 85.1 Thermal Value, B.t.u./1b 18, 587 Aniline-Gravity Constant 6, 444 6, 539 Distillation, Kerosene:

Over Point, F- 330 338 End Poin F 524 526 10% Evap. at. 372 374 50% Evap. at- 420 421 90% Evap. at- 484 479 10 ample, the 0.11:1 weight ratio copolymer of diallyl nonylboronate and lauryl methacrylate, the 0.11:1 Weight ratio copolymer of diallyl phenylboronate and lauryl methacrylate, the 0.12:0.12zl weight ratio terpolymer of diallyl cyclohexylboronate, di(Oxo-octyl)aminoethyl methacrylate and lauryl methacrylate, and the 0.12:0.l2:1 weight ratio terpolymer of bis(2-methylbutenyl) butylboronate, di(OXo-octyl)aminoethyl methacrylate and lauryl methacrylate have been tested for thermal stabilizing properties in the proportion of 20* pounds per thousand barrels of fuel with good results. In addition, for the copolymers of the preceding specific embodiments there can be substituted in proportions of, for example 10 or 20 pounds per thousand barrels of fuel, the 0.05:0.0521, the 0.1:0.l:1, the 0.5:0.5:1 and the 1:1:1 weight ratio copolymers of divinyl butylboronate, butyl allyl butylboronate or dicrotonyl nonylboronatei laurylaminoethyl acrylate, octadecylaminoethyl methacrylate, distearyldimethylammonium methacrylate, laurylbenzyldimethylammonium methacrylate, or dioctylammonium methacrylate; and octyl acrylate, vinyl stearate, vinyl lauryl ether or diisobutylene.

Table Fuel 1 Fuel 2 Refer- Reier- A B O D E F ence ence Make-Up: Percent by Vol.:

Aviation Turbine Fuel 1 100 100 100 100 Aviation Turbine Fuel 2 100 100 100 100 Oopolymer Added, Lbs/1,000 Bb1s.

A. 0.12:0.1221 Wt. Ratio Terpolyrner of Diallyl Nonylboron ate: Diethyla-minoethyl Methacrylate: Lauryl Methacrylate 20 B. 0.12:0.1221 Wt. Ratio Terpolymer of Diallyl Nonylboronate:Di(Oxo-octyl)-aminoethyl Methacrylate:Lauryl Methacry 20 G. 0.14:0.28:1 Wt. Ratio Terpolymer of Diallyl N onylboronate: Di (Oxo-octyl) -aminoethy1 MethacrylatezLauryl Methacrylate 20 D. 0.12:0.12:1 Wt. Ratio Terpolymer oi Diallyl Phenylboronate Di(Oxo-octyl) -an1inoethyl Methacrylate:Lauryl Methacrylate 20 E. 0.l2:0.l2;1 Wt. Ratio Terpolymer of Diallyl Butylboronate:Di(Oxo-octyl)-aminoethyl MethacrylatezLauryl Methacrylatp 20 F. 0.25:1 Wt. Ratio Oopolymer of Diallyl Cyclohexylboronate: Lauryl Methacry 20 Inspections:

OFR Fuel (Joker Test Filter Section, 500 F.:

Time to ReaehaIressure Drop 0f10 In. HgzMin- 60 75 300 300 300 300 300 300 Time to Reach a Pressure Drop of In. HgzMin. 76 95 300 300 300 300 300 300 Pressure Drop at 300 Min: In. Hg. 25 25 0.10 0.00 0.10 0.00 0.10 0. 80 Preheater Section, 410 F.:

Preheater. Deposit, Average Rating (0 Perfect)- 1. 8 l. 9 1.4 0.3 0.8 0.2 1. 5 1.7

From a companson of the test results obtained for The hydrocarbon fuel compositions of this invention Copolymers A, B, and C withthose obtained for Aviation Turbine Fuel 1, and from a comparison of the test results obtained for Copolymers D, E, and F with those obtained for Aviation Turbine Fuel 2, it will be seen that the copolymers of this invention elfected a marked reduction in filter deposits, as evidenced by the virtual elimination of a pressure difierential across the filter, and effected a marked reduction in preheater deposits, as evidenced by a substantially reduced average preheater deposit rating. Comparison of the test results obtained with Copolymers D and E with those obtained with Copolymer F indicates that the herein-disclosed terpolymers are more effective thermal stabilizers, both with respect to filter deposits and with respect to preheater deposits, than the binary copolymers disclosed herein. It is emphasized that the fact that the hereindescribed copolymers are effective to reduce deposits both in the preheater section as well as in the filter section is unusual, since in most instances inhibitors that are eifective to reduce deposits in one section are relatively inefiective to reduce deposits in the other.

It will be understood that the invention is not limited to the particular copolymers described in the preceding specific embodiments, and that other materials disclosed herein can also be employed with good results. For excan also contain various other addition agents adapted to improve one or more properties of the fuel. For example, these compositions can contain in addition to the copolymers disclosed herein, corrosion inhibitors, freezing point depressants,antioxidants, metal deactiva tors, combustion and/or ignition improvement agents and the like. When additional control of heat transfer surface deposits is desired, the fuel compositions of this invention can also contain supplemental preheater deposit inhibitors, such as N,N'-disalicylidene-l,2-propyl enediamine, polyglycerol oleate, or diglycol monolaurate.

The term barrel 'is used herein in its normal sense as applied in the petroleum industry. Hackhs Chemical Dictionary, Third Ediiton, defines the term barrel as applied to petroleum as a unit of volume amounting to '42 gallons.

Many modifications and variations of the invention as herein-described will suggest themselves to those skilled in the, art, and resort may be had to such modifications of a normally thermally unstable liquid hydrocarbon mixture boiling in the aviation turbine fuel range and a small amount, sufficient to improve the thermal stability of said fuel composition, of an oil-soluble boroncontaining copolymer of monomeric components each containing a copolymerizable ethylenic linkage, one of which monomeric components is a boron-free ester of an alpha-beta unsaturated carboxylic acid containing 3 to 5 carbon atoms whose ester substituent is an oleophilic saturated aliphatic hydrocarbon substituent containing 8 to 18 carbon atoms, where another of said monomeric components is a diester of a boronic acid whose boronyl substituent is a hydro carbon radical containing 2 to 18 carbon atoms, said diester having as at least one of its ester substituents an unsaturated aliphatic hydrocarbon radical containing 2 to 12 carbon atoms and an ethylenic linkage that is copolymerizable with the corresponding linkage of said boron-free monomeric component, and having as its other ester substituent a hydrocarbon radical containing 1 to 18 carbon atoms, and where another of said monomeric components contains an organic nitrogenous substituent that does not of itself form a part of the copolymer linkage, said nitrogenous substituent being associated with the group containing the copolymerizable ethylenic linkage through a linkage selected from the group consisting of ester, amine addition salt, amido and quaternary ammonium linkages, at least one of the N-substituents of said organic nitrogenous substituent being a hydrocarbon radical containing 1 to 18 carbon atoms, and the other of said N-substituents being selected from the group consisting of hydrogen and hydrocarbon radicals containing 1 to 18 carbon atoms, said boron-containing monomeric component and said nitrogenous monomeric component being present in the copolymer in a weight ratio of about 0.03 to 1:1 with respect to said boron-free monomeric component.

2. The composition of claim 1 where said small amount is about 2.5 to 50 pounds of said copolymer per thousand barrels of said hydrocarbon mixture.

3. The composition of claim 1 where said small amount is about to 20 pounds of said copolymer per thousand barrels of said hydrocarbon mixture.

4. A fuel composition comprising a major amount of a normally thermally unstable liquid hydrocarbon mixture boiling in the aviation turbine fuel range and a small amount, sufiicient to improve the thermal stability of said fuel composition, of an oil-soluble boroncontaining copolymer of monomeric components each containing a copolymerizable ethylenic linkage, one of which monomeric components is boron-free and is a higher fatty ester of a lower alpha-beta unsaturated monocarboxylic acid containing 3 to 5 carbon atoms, where another of said monomeric components is a diester of a boronic acid whose boronyl substituent is a member selected from the group consisting of saturated aliphatic hydrocarbon radicals and aryl radicals containing 6 to 18 carbon atoms and whose ester substituents are alkenyl radicals containing 2 to 4 carbon atoms, and where another of said monomeric components is a nitrogenous member selected from the group consisting of esters of a lower alpha-beta unsaturated monocarboxylic acid containing 3 to 5 carbon atoms and an alkylolamine Whose alkylol group contains 2 to 4 carbon atoms, said boron-containing monomeric component and said nitrogenous monomeric component being present in the copolymer in a weight ratio of about 0.05:1 to 0.75:1 with respect to said boron-free monomeric component.

5. A fuel composition comprising a major amount of a normally thermally unstable liquid hydrocarbon mixture boiling in the aviation turbine fuel range and containing a small amount, sufficient to improve the thermal stability of the fuel composition, of an oil-soluble boroncontaining copolymer of monomeric components each containing a copolymerizable ethylenic linkage, one of which monomeric components is a boron-free ester of an alpha-beta unsaturated carboxylic acid containing 3 to 5 carbon atoms whose ester substituent is an oleophilic saturated aliphatic hydrocarbon substituent containing 8 to 18 carbon atoms, where another of said monomeric components is a diester of a boronic acid whose boronyl substituent is a hydrocarbon radical containing 2 to 18 carbon atoms, said diester having as at least one of its ester substituents an unsaturated aliphatic hydrocarbon radical containing 2 to 12 carbon atoms and an ethylenic linkage that is copolymerizable with the corresponding linkage of said boron-free monomeric component, and having as its other ester substituent a hydrocarbon radical containing 1 to 18 carbon atoms, said boron-containing monomeric component being present in the copolymer in a weight ratio of about 0.03 to 1:1 with respect to said boron-free monomeric component.

6. A fuel composition comprising a major amount of a liquid hydrocarbon mixture boiling in the aviation turbine fuel range and containing a small amount, sufiicient to improve the thermal stability of the fuel composition, of an oil-soluble boron-containing copolymer of monomeric components each containing a copolymerizable ethylenic linkage, one of which monomeric components is boron-free and is a higher fatty ester of a lower alpha-beta unsaturated monocarboxylic acid containing 3 to 5 carbon atoms, and where another of said monomeric components is a diester of a boronic acid whose boronyl substituent is a member selected from the group consisting of saturated aliphatic hydrocarbon radicals and aryl radicals containing 6 to 18 carbon atoms and whose ester substituents are alkenyl radicals containing 2 to 4 carbon atoms, said boron-containing monomeric component being present in the copolymer in a weight ratio of about 0.05 :1 to 0.75:1 with respect to said boron-free monomeric component.

7. A fuel composition comprising a major amount of a normally thermally unstable liquid hydrocarbon mixture boiling in the aviation turbine fuel range and a small amount, sufficient to improve the thermal stability of said fuel composition, of an oil-soluble boroncontaining copolymer of lauryl methacrylate, diallyl butylboronate, and dioctylaminoethyl methacrylate, the diallyl butylboronate and the dioctylaminoethyl methacrylate being present in the copolymer in a weight ratio of about 0.03 to 1:1 with respect to the lauryl methacrylate.

8. A fuel composition comprising a major amount of a normally thermally unstable liquid hydrocarbon mixture boiling in the aviation turbine fuel range and a small amount, sufficient to improve the thermal stability of said fuel composition, of an oil-soluble boroncontaining copolymer of lauryl methacrylate, bis- (2 -methylbutenyl) butylboronate, and dioctylaminoethyl methacrylate, said bis(Z-methylbutenyl)butylboronate and said dioctylaminoethyl methacrylate being present in the copolymer in a weight ratio of about 0.03 to 1:1 with respect to said lauryl methacrylate.

9. A fuel composition comprising a major amount of a normally thermally unstable liquid hydrocarbon mixture boiling in the aviation turbine fuel range and a small amount, sufficient to improve the thermal stability of said fuel composition, of an oil-soluble boroncontaining copolymer of lauryl methacrylate, diallyl nonylboronate, and diethylaminoethyl methacrylate, where the diallyl nonylboronate and the diethylaminoethyl methacrylate are present in the copolymer in a weight ratio of about 0.05:1 to 0.75:1 with respect to said lauryl methacrylate.

10. A fuel composition comprising a major amount of a normally thermally unstable liquid hydrocarbon mixture boiling in the aviation turbine fuel range and a small amount, sufficient to improve the thermal stability of said fuel composition, of an oil-soluble boroncontaining copolymer of lauryl methacrylate, diallyl nonylboronate, and dioctylaminoethyl methacrylate,

ii L where the diallyl nonylboronate and the dioctylaminoethyl methacrylate are present in the copolymer in a weight ratio of about 0.05 :1 to 0.75 :1 with respect to said lauryl methacrylate.

11. A fuel composition comprising a major amount of a normally thermally unstable liquid hydrocarbon mixture boiling in the aviation turbine fuel range and a small amount, sufiicient to improve the thermal stability of said fuel composition, of an oil-soluble boroncontaining copolymer of lauryl methacrylate, diallyl phenylboronate, and dioctylaminoethyl methacrylate, Where the diallyl phenylboronatc and the dioctylarninoethyl methacrylate are present in the copolymer in a weight ratio of about 0.05:1 to 0.75:1 with respect to said lauryl methacrylate.

12. A fuel composition comprising a major amount of a normally thermally unstable liquid hydrocarbon mixture boiling in the aviation turbine fuel range and a small amount, sufficient to improve the thermal stability of said fuel composition, of an oil-soluble boroncontaining copolymer of lauryl methacrylate, diallyl cyclohexylboronate, and dioctylaminoethyl methacrylate, where the diallyl cyclohexylboronate and the dioctylaminoethyl methacrylate are present in the copolymer in a weight ratio of about 0.05 :1 to 0.75 :1 with respect to said lauryl methacrylate.

13. A fuel composition comprising a major amount of a normally thermally unstable liquid hydrocarbon mixture boiling in the aviation turbine fuel range and a 7 small amount, sufi'icient to improve the thermal stability of said fuel composition, of an oil-soluble boroncontaining copolymer of lauryl methacrylate and diallyl nonylboronate, where the diallyl nonylboronate is present in the copolymer in a weight ratio of about 0.05 :1 to 0.75:1 with respect to the lauryl methacrylate.

14. A fuel composition comprising a major amount of a normally thermally unstable liquid hydrocarbon mixture boiling in the aviation turbine fuel range and a small amount, suflicient to improve the thermal stability of said fuel composition, of an oil-soluble boroncontaining copolymer of lauryl methacrylate and diallyl phenylboronate, where the diallyl phenylboronate is present in the copolymer in a weight ratio of about 0.05 :1 to 0.75:1 With respect to the lauryl methacrylate.

15. A fuel composition comprising a major amount of a normally thermally unstable liquid hydrocarbon mixture boiling in the aviation turbine fuel range and a small amount, sutficient to improve the thermal stability of said fuel composition, of an oil-soluble boroncontaining copolymer of lauryl methacrylate and diallyl cyclohexylboronate, where the diallyl cyclohexylboronate is present in the copolymer in a weight ratio of about 0.05 :1 to 0.75 :1 with respect to the lauryl'methacrylate.

2,974,025 Ertelt et a1 Mar. 7, 1961 Hofl'man Apr. 5, 1960- 

1. A FUEL COMPOSITION COMPRISING A MAJOR AMOUNT OF A NORMALLY THERMALLY UNSTABLE LIQUID HYDROCARBON MIXTURE BOILING IN THE AVIATION TURBINE FUEL RANGE AND A SMALL AMOUNT, SUFFICIENT TO IMPROVE THE THERMAL STABILITY OF SAID FUEL COMPOSITION, OF AN OIL-SOLUBLE BORONCONTAINING COPOLYMER OF MONOMERIC COMPONENTS EACH CONTAINING A COPOLYMERIZABLE ETHYLENIC LINKAGE, ONE OF WHICH MONOMERIC COMPONENTS IS A BORON-FREE ESTER OF AN ALPHA-BETA UNSATURATED CARBOXYLIC ACID CONTAINING 3 TO 5 CARBON ATOMS WHOSE ESTER SUBSTITUENT IS AN OLEPHILIC SATURATED ALIPHATIC HYDROCARBON SUBSTITUENT CONTAINING 8 TO 18 CARBON ATOMS, WHERE ANOTHER OF SAID MONOMERIC COMPONENTS IS A DIESTER OF A BRONIC ACID WHOSE BORONYL SUBSTITUTENT IS A HYDRO CARBON RADICAL CONTAINING 2 TO 18 CARBON ATOMS, SAID DIESTER HAVING AS AT LEAST ONE OF ITS ESTER SUBSTITUENTS AN UNSATURATED ALIPHATIC HYDROCARBON RADICAL CONTAINING 2 TO 12 CARBON ATOMS AND AN ETHYLENE LINKAGE THAT IS COPOLYMERIZABLE WITH THE CORRESPONDING LINKAGE OF SAID BORON-FREE MONOMERIC COMPONENT, AND HAVING AS ITS OTHER ESTER SUBSTITUENT A HYDROCARBON RADICAL CONTAINING 1 TO 18 CARBON ATOMS, AND WHERE ANOTHER OF SAID MONOMERIC COMPONENTS CONTAINS AN ORGANIC NITROGENOUS SUBSTITUENT THAT DOES NOT OF ITSELF FORM A PART OF THE COPOLYMER LINKAGE, SAID NITROGENOUS SUBSTITUENT BEING ASSOCIATED WITH THE GROUP CONTAINING THE COPOLYMERIZABLE ETHYLENIC LINKAGE THROUGH A LINKAGE SELECTED FROM THE GROUP CONSISTING OF ESTER, AMINE ADDITION SALT. AMIDO AND QUATERNARY AMMONIUM LINKAGES, AT LEAST ONE OF THE N-SUBSTITUENTS OF SAID ORGANIC NITROGENOUS SUBSTITUENT BEING A HYDROCARBON RADICAL CONTAINING 1 TO 18 CARBON ATOMS, AND THE OTHER OF SAID N-SUBSTITUENTS BEING SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND HYDROCARBON RADICALS CONTAINING 1 TO 18 CARBON ATOMS, SAID BORON-CONTAINING MONOMERIC COMPONENT AND SAID NITROGENOUS MONOMERIC COMPONENT BEING PRESENT IN THE COPOLYMER IN A WEIGHT RATIO OF ABOUT 0.03 TO 1:1 WITH RESPECT TO SAID BORON-FREE MONOMERIC COMPONENT. 